Reactor having dynamic sparger

ABSTRACT

Systems and methods relating to dynamic spargers for generating fine bubbles within reactors such as biological and chemical reactors. A sparger system is positioned within a reactor and comprises a support plate, multiple annular shrouds engaged with the support plate, and spargers positioned within the annular shrouds defining a gap between an interior surface of the annular shroud and an exterior surface of the corresponding sparger. Liquid flows through the defined gap between an interior surface of the annular shroud and an exterior surface of the sparger. Acceleration of the liquid through the gap shears bubbles at the exterior surface of the sparger creating bubbles or fine bubbles.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication No. 63/263,507, filed Nov. 3, 2021, the entirety of which isincorporated herein by reference.

FIELD

Embodiments described herein generally relate to systems and methods forthe injection of gas bubbles into a liquid. In particular, systems andmethods disclosed herein generally relate to dynamic spargers forgenerating and injecting bubbles or fine bubbles into a liquid brothwithin a chemical or biological reactor. Further, systems and methodsare disclosed herein for the injection of gaseous carbon-substrate finebubbles within a bioreactor containing liquid microorganism culturesthat biologically ferment the carbon substrate for the production of auseful product such as ethanol or other chemicals.

BACKGROUND

A sparger is a device that injects gas into a liquid. Gas injected intothe liquid from a sparger forms bubbles in the liquid. Conventionalsystems employing spargers for the generation and injection of gasbubbles into liquids during industrial process are well-known. Tomaximize the conversion of gas substrates injected into liquids touseful fermentation products in bioreactors, spargers need to producesmall bubbles with increased gas flow rates through the sparger.Conventional sparger systems, however, cannot achieve the required smallbubble size because bubble size at the sparger increases with increasedgas flow rates. As such, what is needed is a sparger system that cangenerate fine bubbles at higher gas flow rates in bioreactors to achievehigh productivity. Additionally, previous “frit and sleeve” spargersystems comprising porous ring (frit) surrounded by a sleeve throughwhich liquid is passed are typically external to reactors resulting ininefficient configurations and increased footprint requirements.

The sparger systems disclosed herein overcome the limitations ofprevious and conventional reactor systems. Specifically, the spargersystem and methods of injecting substrate feed gas into the aqueousbroth of a reactor, such as a bioreactor, as disclosed herein, achievessmall bubble size, increased gas flow rates through the sparger, andhigher superficial gas and liquid velocities for high reactor/bioreactorproductivity. Further, the sparger systems disclosed herein areconfigured entirely within the reactor in contrast to previous systems.

SUMMARY

The following presents a simplified summary of various embodimentsdescribed herein. This summary is not an extensive overview and is notintended to identify key or critical elements or to delineate the scopeof the claims. The following summary merely presents some concepts in asimplified form as an introductory prelude to the more detaileddescription provided below.

To overcome limitations in previous systems described above, and toovercome other limitations that will be apparent upon reading andunderstanding the present specification, embodiments described hereinare directed to systems and methods for the efficient injection ofbubbles into a liquid contained within biological and chemical reactors.

In one embodiment, the systems disclosed herein relate to injectingbubbles into a liquid. The system may include a support plate, aplurality of annular shrouds engaged with the support plate, and aplurality of spargers positioned within the annular shrouds. In someembodiments the support plate and at least one annular shroud areintegrated into a single component. In some embodiments, a gap may bedefined between the shroud interior surface and the sparger exteriorsurface. In certain embodiments, the support plate, the annular shrouds,and the spargers may be positioned completely within the interior of areactor. In certain embodiments, the length of the spargers may be atleast 10 cm, and the width of the gap between the shroud interiorsurface and the sparger exterior surface may be about 1 mm to about 20mm. In other embodiments, the support plate, the annular shrouds, andthe spargers may be positioned at a top portion or at a bottom portionof the reactor. The plurality of spargers may engage a plurality ofheaders, and the plurality of spargers may be configured to receive agas supply from the plurality of headers. In certain embodiments, theplurality of headers may further include a baffle configured to dispersea fluid comprising the liquid and bubbles. In yet other embodiments, theliquid may be at least partially recirculated liquid. In certainembodiments, the support plate further includes a plurality ofperforations, and the annular shrouds may be positioned within about 20degrees of a vertical axis of the reactor. In one embodiment, aplurality of support plates may form multiple layers or levels withinthe interior of the reactor, and the plurality of support plates mayinclude a plurality of annular shrouds, and a plurality of spargers maybe positioned within the plurality of annular shrouds.

In one embodiment, the reactor may be a bioreactor including a liquidgrowth medium and a substrate comprising at least one C1 carbon source.In certain embodiments, the plurality of spargers may be configured toinject substrate bubbles into the liquid growth medium. In otherembodiments, the bioreactor may also include a culture of at least onemicroorganism in the liquid growth medium, and the culture of at leastone microorganism may anaerobically ferment the substrate to produce atleast one fermentation product.

In still another embodiment, the systems and methods disclosed hereinrelate to a method of sparging bubbles into a liquid that may includethe steps of sparging gas into a reactor containing a liquid via aplurality of spargers positioned within the reactor and configured toemit bubbles, directing a flow of the liquid across an exterior surfaceof the spargers via a plurality of annular shrouds within the reactorand surrounding the plurality of spargers, and shearing the bubbles at asurface of the plurality of spargers via the flow of the liquid acrossthe exterior surface of the spargers. In certain embodiments, the methodmay further include accelerating the flow of the liquid across theexterior surface of the spargers via a gap formed between an interiorsurface of the annular shrouds and the exterior surface of the spargers.In some embodiments, the accelerated flow of the liquid across theexterior surface of the spargers may have a superficial liquid velocityof at least 0.3 m/s, and the accelerated flow of the liquid across theexterior surface of the plurality of spargers may have a velocity ofabout 0.3 m/s to about 10 m/s. In still other embodiments, the shearedbubbles may have a diameter of about 0.2 mm to about 2.0 mm, and thesuperficial velocity of a gas phase in the vessel may be at least 0.03m/s. In one embodiment, the superficial velocity of the gas phase in thevessel may be about 0.03 m/s to about 0.1 m/s. In yet anotherembodiment, the bubbles may be substrate bubbles within a bioreactorthat may contain a liquid growth medium. In other embodiments, a cultureof at least one microorganism in the liquid growth medium mayaerobically ferment the substrate to produce at least one fermentationproduct.

These features, along with many others, are discussed in greater detailbelow.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of embodiments described herein, and theadvantages thereof may be acquired by referring to the followingdescription in consideration of the accompanying drawings, in which likereference numbers indicate like features, and wherein:

FIG. 1 schematically depicts a dynamic sparger arrangement configuredwithin a reactor showing downflow mode of liquid and bubbles inaccordance with one embodiment of the disclosure.

FIG. 2 schematically depicts an alternative dynamic sparger arrangementwithin a reactor showing upflow mode of liquid and bubbles in accordancewith another embodiment of the disclosure.

FIG. 3 schematically depicts a bioreactor system including one or moredynamic sparger system arrangements and their various locations withinthe bioreactor, according to yet another embodiment of the disclosure.

FIG. 4 schematically depicts an alternative dynamic sparger arrangementwithin a reactor showing horizontally positioned sparges and an upflowmode of liquid and bubbles in accordance with another embodiment of thedisclosure.

FIG. 5 schematically depicts an alternative dynamic sparger arrangementwithin a reactor showing bundles of horizontally positioned sparges andan upflow mode of liquid and bubbles in accordance with anotherembodiment of the disclosure.

FIG. 6 schematically depicts the device of FIG. 5 in a top view frompoint 525 of FIG. 5 .

DETAILED DESCRIPTION

In the following description of the various embodiments, reference ismade to the accompanying drawings, which form a part hereof, and inwhich is shown by way of illustration various embodiments describedherein may be practiced. It is to be understood that other embodimentsmay be utilized, and structural and functional modifications may be madewithout departing from the scope of the described embodiments.Embodiments described herein are capable of other embodiments and ofbeing practiced or being carried out in various ways. Also, it is to beunderstood that the phraseology and terminology used herein are for thepurpose of description and should not be regarded as limiting. Rather,the phrases and terms used herein are to be given their broadestinterpretation and meaning. The use of “including” and “comprising” andvariations thereof is meant to encompass the items listed thereafter andequivalents thereof as well as additional items and equivalents thereof.The use of the terms “mounted,” “connected,” “engaged,” “fluidlyengaged,” “coupled,” “positioned,” “configured,” “oriented,” and similarterms, is meant to include both direct and indirect mounting,connecting, coupling, positioning, and engaging.

A sparger may comprise a device to introduce a gas into a liquid,injected as bubbles, to agitate it or to dissolve the gas in the liquid.Example spargers may include orifice spargers, sintered spargers, anddrilled pipe spargers. In certain configurations, drilled pipe spargersmay be mounted horizontally. In other embodiments, spargers may bemounted vertically or horizontally. In some embodiments, the sparger maybe a perforated plate or ring, sintered glass, sintered steel, porousrubber pipe, porous metal pipe, porous ceramic, or stainless-steel pipe,drilled pipe, stainless steel drilled pipe, polymeric drilled pipe, etc.The sparger may be of various grades (porosities) or may include certainsized orifices to produce a specific sized bubble or range of bubblesizes.

The systems and methods, as disclosed herein, employ a spargerarrangement for generation of fine bubbles, increasing the gas flowrates through the sparger, and increasing superficial gas velocity andsuperficial liquid velocity for high reactor productivity. Increasingreactor productivity may be achieved by increasing the amount of gassubstrate injected into the liquid broth and available for microbefermentation, and by increasing the specific interfacial area which isdefined as the total surface area of the bubbles in unit volume of thereactor. Specific interfacial area is inversely proportional to thebubble size and directly proportional to gas hold up, where gas hold upis the volume of gas present in a unit volume of fluid having bubblesdispersed therein. Reduction of bubble size by generating fine bubblesincreases the specific interfacial area. Increased specific interfacialarea enhances gas to liquid mass transfer. In embodiments, where thereactor is a bioreactor, enhanced gas to liquid mass transfer ultimatelyprovides microorganisms with increased amounts of substrate gas toconvert into useful fermentation products such as ethanol and otherchemicals. Example of systems and methods used to create bubbles includethose described in U.S. Pat. No. 9,327,251 hereby incorporated byreference in its entirety for all purposes. Higher reactor productivitymay also be achieved by higher gas hold up which is related to increasedoverall superficial gas velocity and superficial liquid velocity in thereactor. Increased superficial gas velocity and superficial liquidvelocity may be used to break or shear sparger bubbles into a desiredfine bubble size. In downflow operation, fine bubbles experience abuoyancy force which is less than a drag force imparted by the liquidand hence overall fluid downflow is created to carry the fine bubblesand the liquid downward in the reactor. The fluid downflow helpsincrease residence time of the microorganisms in the liquid and extendsthe time for microorganisms to convert fine bubbles of substrate in thebioreactor to desired products.

The sparger system, as disclosed herein, may employ a plate engaged withan array of chimney shroud tubes, or annular shrouds, and cylindricalspargers configured entirely within the reactor. Generally, the innerdiameter of the annular shrouds may be slightly larger than the outerdiameter of the cylindrical spargers configured within the annularshrouds. As liquid is pumped through the system, the liquid is forced topass through a restricted space, or gap, between the sparger and theannular shrouds. The liquid is accelerated as it passes through the gapand increases the shear rate provided by the liquid near the surface ofthe spargers. The increased shear rate reduces the bubble size of gasinjected into the liquid from the spargers and creates fine bubbles.

FIG. 1 schematically depicts a bioreactor system 100 comprising reactor102. Bioreactor system 100 may include any device capable of being usedfor a fermentation process or a chemical conversion process. Reactor 102may be a vessel or container in which one or more gas and liquid streamsor flows 101 may be introduced for bubble generation and/or fine bubblegeneration, and for subsequent gas-liquid contacting, gas-absorption,biological or chemical reaction, such as for example, microbialfermentation. The term “microbial fermentation” or “fermentation” or“gas fermentation” and the like may be interpreted as the process whichreceives one or more gaseous substrates and produces one or morefermentation products through the utilization of one or more C1-fixingmicroorganisms. The gaseous substrate may be from an industrial process,or may be syngas, or any combination thereof. Syngas may be obtainedfrom a reforming, partial oxidation, or gasification process. A“C1-fixing microorganism” is a microorganism or microbe that producesone or more fermentation products from a C1-carbon source. Typically,the microorganism of the disclosure is a C1-fixing bacterium. The“C1-carbon source” refers a one carbon-molecule that serves as a partialor sole carbon source for the microorganism. For example, the C1-carbonsource may comprise one or more of CO, CO₂, CH₄, CH₃OH, or CH₂O₂. In anembodiment, the C1-carbon source comprises one or both of CO and CO₂.The fermentation process may include the use of one or more bioreactors.The phrases “fermenting,” “fermentation process” or “fermentationreaction” and the like, as used herein, are intended to encompass boththe growth phase and product biosynthesis phase of the gaseoussubstrate. Examples of C1-fixing microorganisms may include Moorella,Clostridium, Ruminococcus, Acetobacterium, Eubacterium, Butyribacterium,Oxobacter, Methanosarcina, Desulfotomaculum, Clostridiumautoethanogenum, and combinations thereof. In one embodiment, the C1fixing microorganism is Clostridium autoethanogenum, Clostridiumljungdahlii, or Clostridium ragsdalei.

In some embodiments, liquid 101 is recycled within the system 100. Afluid, as disclosed herein, may include liquid, bubbles, and/or finebubbles. Fermentation broth or liquid 101 may encompass any mixture ofcomponents disclosed herein, for example, a nutrient media and a cultureor one or more microorganisms. The fermentation process may utilize thefermentation broth to ferment the substrate gas bubbles or fine bubblesto one or more fermentation products. The bacterial culture may bemaintained in an aqueous culture medium that contains nutrients,vitamins, and/or minerals sufficient to permit growth of themicroorganism. Bioreactor system 100 may consist of one or more reactors102 and/or towers or piping arrangements. Suitable bioreactors include,for example, a continuous stirred tank reactor (CSTR), immobilized cellreactor (ICR), trickle bed reactor (TBR), bubble column, gas liftfermenter, static mixer, a circulated loop reactor, a membrane reactor,such as a hollow fiber membrane bioreactor (HFM BR) or other vessel orother device suitable for gas-liquid contact.

Reactor 102 may not be restricted to any specific embodiment, such asheight to diameter ratio, or restricted to any specific material and canbe constructed from any material suitable to the process such asstainless steel or PVC. Reactor 102 may contain internal components suchas one or more static mixers that are common in biological and chemicalengineering processing. Reactor 102 may also consist of external orinternal heating or cooling elements such as water jackets. Reactor 102may also be in fluid contact with a pump to circulate or recirculateliquid, bubbles, fine bubbles, and/or fluid 101, 101 a, and 111 ofsystem 100. The dimensions of the components of bioreactor system 100,as depicted in FIG. 1 , may vary depending upon the required use orprocess. According to certain embodiments, the diameter of reactor 102may be, for example, at least, greater than, less than, equal to, or anynumber in between about 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5,5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, 10.0, 10.5, 11.0,11.5, 12.0, 12.5, 13.0, 13.5, 14.0, 14.5, 15.0, 15.5, 16.0, 16.5, 17.0,17.5, 18.0, 18.5, 19.0, 19.5 to about 20.0 meters. According to otherembodiments, the length of reactor 102 may be, for example, at least,greater than, less than, equal to, or any number in between about 5.0,5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, 10.0, 10.5, 11.0, 11.5,12.0, 12.5, 13.0, 13.5, 14.0, 14.5, 15.0, 15.5, 16.0, 16.5, 17.0, 17.5,18.0, 18.5, 19.0, 19.5, 20.5, 21.5, 22.0, 22.5, 23.0, 23.5, 24.0, 24.5,25.0, 26.0, 27.0, 28.0, 29.0, 30.0, 31.0, 32.0, 33.0, 34.0, 35.0, 36.0,37.0, 38.0, 39.0, 40.0, 41.0, 42.0, 43.0, 44.0, 45.0, 46.0, 47.0, 48.0,49.0 to about 50.0 meters.

In reactor 102, the gas and liquid phases, for example, fluid 111, mayflow or be circulated in the vertical directions to include generallydownward flow or, for example, generally upward flow as shown in FIG. 2. As shown in reactor 102 of FIG.1, gas and liquid phases in fluid 111may flow generally downward within reactor 102. The superficial liquidvelocity, V_(L), in the reactor may be calculated by the followingequation VL=Q_(L)/A_(C) where Q_(L) is the volumetric flow rate of theliquid (m³/s), and A_(C) is the cross-sectional area of the reactor.Therefore, superficial liquid velocity represents velocity of the liquidphase if it occupied the entire cross-sectional area of the reactor. Forthe same liquid flow rate, the gas flow rate can vary depending on theactual application. Superficial velocity of the gas phase V_(G) may bedetermined by the following equation V_(G)=Q_(G)/A_(C) where Q_(G) isthe volumetric flow rate of the gas (m³/s) injected into the liquid fromthe sparger(s) and A_(C) is the cross-sectional area of the reactor.Therefore, superficial gas velocity represents velocity of the gas phaseif it occupied the entire cross-sectional area of the reactor. In someembodiments, the superficial velocity of the gas phase in the vessel maybe at least 0.03 m/s. In other embodiments, superficial velocity of thegas phase in the vessel is about 0.03 m/s to about 0.1 m/s. In stillother embodiments, the superficial velocity of the gas phase in thevessel may be, for example, at least, greater than, less than, equal to,or any number in between about 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07,0.08, 0.09, 0.10, 0.12, 0.13, 0.14 to about 0.15 m/s. In yet anotherembodiment, the superficial velocity of the gas phase in the vessel maybe, for example, approximately 0.03 to 0.06 m/s. In one embodiment, thesuperficial liquid velocity may be at least about 0.3 m/s. As discussedabove, increasing the superficial gas velocity and the superficialliquid velocity has the beneficial effect of breaking or shearing thesparger bubbles into the desired fine bubble size.

Bioreactor system 100 may include at least one sparger 106 to introducea gas substrate into liquid 101, injected as bubbles, to agitate the gasor to dissolve the gas in the liquid 101. Sparger 106 may be mounted ina horizontal or a vertical position. In some embodiments, the sparger106 may be an orifice sparger, sintered sparger, or drilled pipesparger, a perforated plate or ring, sintered glass, sintered steel,porous rubber pipe, porous metal pipe, porous ceramic or stainless-steelpipe, drilled pipe, stainless steel drilled pipe, or polymeric drilledpipe. Sparger 106 may be of various grades (porosities) or may includecertain sized orifices to produce a specific sized bubble. Porosity ofspargers are generally designed to avoid weeping which arises wheninsufficient kinetic energy of the gas flowing through the pores isunable to support the liquid head above the sparger pores. Operatingvelocity of the gas through the pores is designed substantially higherthan weeping velocity to ensure uniform sparging. Sparger 106 may have alength of, for example, at least, greater than, less than, equal to, orany number in between about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13,14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31,32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49,to about 50 cm. The bioreactor system 100 may be adapted to receive agaseous substrate via header(s) 108 comprising a C1-carbon sourceinjected into the liquid broth 101 as bubbles 103 by sparger 106.

Bioreactor system 100 may include support plate 104. Support plate 104may be configured to engage at least one annular shroud 105. A diameterof the annular shroud 105 may be larger than the diameter of sparger106. Thus, sparger 106 may be configured to be positioned inside annularshroud 105 defining a gap or restricted area 107 between the exteriorwalls of sparger 106 and the interior walls of annular shroud 105. Insome embodiments the width of gap 107 is about 1 to 20 mm. In otherembodiments, the width of gap 107 may be, for example, at least, greaterthan, less than, equal to, or any number in between about 0.25, 0.50,0.75, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19,20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37,38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, to about 50 mm.

Spargers 106 and annular shrouds 105 may be positioned entirely withinthe interior of reactor 102. In some embodiments, support plate 104,annular shrouds 105, and spargers 106 may be positioned at a top orupper portion of reactor 102. Positioning support plate 104, annularshrouds 105, and spargers 106 in an upper portion of reactor 102 mayhave the additional advantage of decreasing hydrostatic pressure at thetop of reactor 102 to facilitate increased gas to liquid mass transferrates with decreased energy requirements. In some embodiments, thesystems and methods disclosed herein achieve gas to liquid mass transferrates of at least 125 m³/min. In other embodiments, the gas to liquidmass transfer rates may be, for example, at least, greater than, lessthan, equal to, or any number in between about 100, 105, 110, 115, 120,125, 130, 135, 140, 145, 150, 155, 160, 165, 170, 175, 180, 185, 190,195 to about 200 m³/min. Alternatively, support plate 104, annularshrouds 105, and spargers 106 may be positioned at a bottom or lowerportion of reactor 102. In still other embodiments, support plate 104,annular shrouds 105, and spargers 106 may be positioned at the upperone-third portion, upper two-thirds portion, or a lower one-thirdportion of reactor 102. In some embodiments, annular shrouds 105 may bemade from standard pipe, seamless tube, welded tube, custom made tube,or combinations thereof. Annular shroud 105 components may be bonded orsecured to support plate 104 by shielded metal arc welding, gas tungstenarc welding, gas metal arc welding, flux-cored arc welding, submergedarc welding, electroslag welding, or fabricated by weldless tube-sheetjoint rolled in place techniques. In other embodiments, silver solderingmay be avoided to prevent damage to microorganisms during fermentation.In still other embodiments, support plate 104 may include perforations109 to facilitate the removal or draining of solid debris. In certainembodiments, a plurality of support plates 104 may form multiplevertical layers within reactor 102. Each vertical layer of supportplates 104 may include a plurality of annular shrouds 105, and aplurality of spargers 106. In still other embodiments, annular shrouds105 may be positioned generally perpendicular to support plate 104. Inother embodiments, the annular shrouds may be positioned, for example,at least, greater than, less than, equal to, or any number in betweenabout 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19,20, 21, 22, 23, 24, 25, 26, 27, 28, 29, to about 30 degrees of avertical axis of reactor 102.

As shown in FIG. 1 , liquid broth 101 enters the top of reactor 102. Gassubstrate is injected into liquid 101 within reactor 102 by sparger(s)106 connected to gas supply/headers 108. At least a portion of the flowof liquid 101 is directed across the exterior surface of spargers 106.In some embodiments, nearly all of the flow of liquid 101 is directedacross the exterior surface of spargers 106. As the liquid 101 is forcedinto gap 107 defined by the annular shroud 105 and the exterior walls ofthe sparger 106, the liquid is accelerated as it travels across avertical length of the spargers 106 and the annular shrouds 105.Accelerated liquid 101 a shears injected bubbles on the surface of thesparger 106 breaking the injected bubbles into fine bubbles 103. Shearedfine bubbles 103 may have a diameter from about 0.2 to about 2.0 mm.According to another embodiment, the diameter of the fine bubbles maybe, for example, at least, greater than, less than, equal to, or anynumber in between about 0.001, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007,0.008, 0.009, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1,0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5,1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9,3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1, 4.2, 4.3,4.4, 4.5, 4.6, 4.7, 4.8, 4.9 to about 5.0 mm. The accelerated flow ofliquid 101 a across the exterior surface of the spargers 106 may have avelocity of at least 0.3 m/s. In another embodiments, the acceleratedflow of liquid 101 a across the exterior surface of the spargers 106 mayhave a velocity of about 0.3 to about 10 m/s. In other embodiments, theaccelerated flow of liquid 101 a across the exterior surface of thespargers 106 may have a superficial liquid velocity of, for example, atleast, greater than, less than, equal to, or any number in between about0.1, 0.15, 0.2, 0.25, 0.3, 0.35 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12,13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29 toabout 30 m/s.

According to other embodiments, spargers 106 may be positioned in abottom portion of reactor 102 or in a middle portion of reactor 102.According to another embodiment, spargers 106 may be oriented in ahorizontal position. According to still another embodiment, spargers 106may be positioned in multiple positions throughout reactor 102 toinclude the upper, middle, and lower portions of reactor 102. Accordingto yet another embodiment, spargers 106 may be a ring sparger or adrilled-pipe sparger. According to one embodiment, individual spargers106 and header 108 may be configured as modular components facilitatingthe ease of reactor construction and/or component replacement, generalmaintenance, cleaning, or allowing for a scalable reactor systemdepending upon the requirements. In accordance with other embodiments,multiple levels of spargers 106 and headers 108 may be stacked withinreactor 102. In still other embodiments, spargers 106 may be configuredto extend vertically below the header 108, or spargers 106 may beconfigured to extend vertically above the header 108. According toanother embodiment, a single level or stack of headers 108 may include,for example, at least, greater than, less than, equal to, or any numberin between about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16,17, 18, 19 to about 20 individual headers 108. In some embodiments,header 108 may be configured as an annular gas supply. In yet anotherembodiment, one or more fluid distributors (not shown) may be employedso that fluid flow 111 is distributed across reactor 102. In oneembodiment, the fluid distributors are positioned near to the fluidexits of gaps 107. The fluid distributors may be impermeable plates orvanes or troughs. The fluid distributors may be attached to a terminalend of spargers 106 and extending below spargers 106 and at leastpartially across an area below gaps 107.

FIG. 2 depicts an alternative arrangement of the sparger system of FIG.1 . As shown in FIG. 2 , the liquid 201 and fluid 211 having both gasphase and liquid phase may flow or be circulated generally in an upwardvertical direction in a loop reactor system. The support plate 204 iscontained within the reactor. Again, support plate 204 may be configuredto engage at least one annular shroud 205. A diameter of the annularshroud 205 may be larger than the diameter of sparger 206. Thus, sparger206 may be configured to be positioned inside annular shroud 205defining a gap or restricted area 207 between the exterior walls ofsparger 206 and the interior walls of annular shroud 205. Spargers 206may be fluidly engaged with header 208 through extensions 213 extendingtherefrom. Header 208 may be configured to receive a gaseous substrateto be injected into liquid broth 201 by spargers 206. Liquid broth 201may enter from a bottom portion the reactor. At least a portion 201 a ofliquid 201 may be directed across the exterior surface of spargers 206.In some embodiments, nearly all of the flow of liquid 201 may bedirected across the exterior surface of spargers 206. As liquid 201 isforced into gap 207 defined by annular shroud 205 and the exterior wallsof sparger 206, liquid 201 is accelerated as it travels verticallyupwards through the gap 207. Accelerated liquid 201 a shears injectedbubbles on the exterior surface of sparger 206 creating fine bubbles203. Vertical extension 213 extended from the header 208 may include abaffle 215 configured to redirect or deflect the flow of fluid 211 toprevent dead zones of stagnant fluid. Support plate 204 may also includeholes or perforations 217 for drainage and circulation for stagnantareas of fluid. In one embodiment, the annular shroud may be disposedwithin a guide to control adjustment of its concentricity with thesparger (not shown).

As depicted in FIG. 2 , the positioning of header 208 above spargers 206is advantageous because the configuration does not interfere with theupward flow of liquid and bubbles. Additionally, the system componentsmay be modular that allows for ease of construction, maintenance, andreplacement of components within the system, to include spargers 106. Insome embodiments, header 208 may be permanently installed in thereactor, and spargers 106 may be subsequently attached to verticalextension 213 and/or header 208. Spargers 206 and vertical extensions213 may be a series of individual pieces/components to be easilytransported and inserted into the reactor vessel and then individuallyconnected with the vessel. Like the system depicted in FIG. 1 , thesystem depicted in FIG. 2 may include a plurality of headers 208, and aplurality of support plates 204 may form multiple vertical layers withinthe reactor. Each vertical layer of support plates 204 may include aplurality of annular shrouds 205, and a plurality of spargers 206fluidly engaged with a plurality of vertical extensions 213 andheader(s) 208. In certain embodiments, the reactor vessel may include,for example, at least, greater than, less than, equal to, or any numberin between about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16,17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34,35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52,53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70,71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88,89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99 to about 100 vertical layersof support plates. In some embodiments, each vertical layer may include,for example, at least, greater than, less than, equal to, or any numberin between about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16,17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34,35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52,53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70,71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88,89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104,105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118,119, 120, 121, 122, 123, 124, 125, 126, 127, 128, 129, 130, 131, 132,133, 134, 135, 136, 137, 138, 139, 140, 141, 142, 143, 144, 145, 146,147, 148, 149, 150, 151, 152, 153, 154, 155, 156, 157, 158, 159, 160,161, 162, 163, 164, 165, 166, 167, 168, 169, 170, 171, 172, 173, 174,175, 176, 177, 178, 179, 180, 181, 182, 183, 184, 185, 186, 187, 188,189, 190, 191, 192, 193, 194, 195, 196, 197, 198, 199 to about 200spargers and/or annular shrouds. Again, such a sparger configuration maybe employed in reactor systems 100 and 200 described in both FIGS. 1 and2 .

According to other embodiments, spargers 206 may be positioned in abottom portion of the reactor or in a middle portion of the reactor.According to another embodiment, spargers 206 may be oriented in ahorizontal position. According to still another embodiment, spargers 206may be positioned in multiple positions throughout the reactor toinclude the upper, middle, and lower portions of the reactor. Accordingto yet another embodiment, spargers 206 may be a ring sparger or adrilled-pipe sparger. According to one embodiment, individual spargers206 and header 208 may be configured as modular components facilitatingthe ease of reactor construction and/or component replacement, generalmaintenance, cleaning, or allowing for a scalable reactor systemdepending upon the requirements. In accordance with other embodiments,multiple levels of spargers 206 and headers 208 may be stacked withinthe reactor. In still other embodiments, spargers 206 may be configuredto extend vertically below the header 208, or spargers 206 may beconfigured to extend vertically above the header 208. According toanother embodiment, a single level or stack of headers 208 may include,for example, at least, greater than, less than, equal to, or any numberin between about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16,17, 18, 19 to about 20 individual headers 208. In some embodiments,header 208 may be configured as an annular gas supply.

FIG. 3 depicts a loop-style bioreactor system 300 incorporating thesparger-shroud systems and methods disclosed herein. Liquid brothcirculating within reactor 304 is injected with gas substrate throughone or both of sparger-shroud assemblies 316 and 306. Exemplary detailsof suitable sparger-shroud assemblies were shown in FIG.1 and FIG. 2 .In one embodiment, at least a portion of the flow of liquid broth 301flowing into riser section 302 of reactor 304 is forced into gapsdefined by the annular shrouds and the exterior walls of the spargers ofsparger-shroud assembly 316. Liquid broth 301 is accelerated as ittravels through the gap defined by the spargers and the annular shroudsof sparger-shroud assembly 316. The accelerated liquid broth 301 shearsinjected bubbles on the surface of the spargers thereby creating finebubbles. Resulting fluid 311 containing the liquid broth and finebubbles flows upwards in the riser section 302 of reactor 304 and exitsriser section 302 into separator section 308. At least a portion offluid 311 passes out of separator section 308 and into downcomer 312. Atthis point, fluid 311 may be depleted of gas substrate and form gassubstrate depleted liquid broth 321. Optionally, downcomer 312 mayinclude at least one sparger-shroud assembly 306 as disclosed herein.Sparger-shroud assembly 306 located within the downcomer 312 may injectfine bubbles of gas substrate into substrate depleted liquid broth 321to provide the microorganisms therein with additional substrate andprolong survival. Bioreactor system 300 may include pump 314 tocirculate liquid broth 301 and fluid 311 and substrate depleted liquidbroth 321 throughout bioreactor system 300.

As shown in FIG. 4 , liquid broth 401 enters the bottom of reactor 402.Gas substrate is injected into liquid 401 within reactor 402 bysparger(s) 406 connected to gas supply/headers 408. At least a portionof the flow of liquid 401 is directed across the exterior surface ofspargers 406. In some embodiments, nearly all of the flow of liquid 401is directed across the exterior surface of spargers 406. In otherembodiment, portions of liquid flow 401 bypasses the exterior surface ofspargers 406 though passages 403. As the liquid 401 is forced into gap407 defined by the annular shroud 405 and the exterior walls of thespargers 406, the liquid is accelerated as it travels across acircumference or vertical surface of the horizontally positionedspargers 406 and the annular shrouds 405. Accelerated liquid 401 ashears injected bubbles on the surface of the spargers 406 breaking theinjected bubbles into fine bubbles 409. Sheared fine bubbles 409 mayhave a diameter from about 0.2 to about 2.0 mm. According to anotherembodiment, the diameter of the fine bubbles may be, for example, atleast, greater than, less than, equal to, or any number in between about0.001, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, 0.01,0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, 0.5,0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9,2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3,3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7,4.8, 4.9 to about 5.0 mm. Fluid flow comprising the fine bubblescontinues in an upflow mode 420. The accelerated flow of liquid 401 aacross the exterior surface of the spargers 406 may have a velocity ofat least 0.3 m/s. In another embodiments, the accelerated flow of liquid401 a across the exterior surface of the spargers 406 may have avelocity of about 0.3 to about 10 m/s. In other embodiments, theaccelerated flow of liquid 401 a across the exterior surface of thespargers 406 may have a superficial liquid velocity of, for example, atleast, greater than, less than, equal to, or any number in between about0.1, 0.15, 0.2, 0.25, 0.3, 0.35 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12,13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29 toabout 30 m/s.

According to other embodiments, spargers 406 may be positioned in abottom portion of reactor 402 or in a middle portion of reactor 402.FIG. 4 shows the embodiment where spargers 406 are oriented in ahorizontal position. According to still another embodiment, spargers 406may be positioned in multiple positions throughout reactor 402 toinclude the upper, middle, and lower portions of reactor 402. Accordingto yet another embodiment, spargers 406 may be a ring sparger or adrilled-pipe sparger. According to one embodiment, individual spargers406 and header 408 may be configured as modular components facilitatingthe ease of reactor construction and/or component replacement, generalmaintenance, cleaning, or allowing for a scalable reactor systemdepending upon the requirements. In accordance with other embodiments,multiple levels of spargers 406 and headers 408 may be stacked withinreactor 402. In still other embodiments, spargers 406 may be configuredto extend horizontally spanning the cross section of reactor 402.According to another embodiment, a single level or stack of headers 408may include, for example, at least, greater than, less than, equal to,or any number in between about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12,13, 14, 15, 16, 17, 18, 19 to about 20 individual headers 408 orvertical extensions 413. In some embodiments, header 408 may beconfigured as an annular gas supply.

As further depicted in FIG. 4 , the positioning of header 408 abovespargers 406 is advantageous because the configuration does notinterfere with the upward flow of liquid and bubbles. In FIG. 4 ,spargers 406 are positioned horizontally within reactor 402.Additionally, the system components may be modular that allows for easeof construction, maintenance, and replacement of components within thesystem, to include spargers 406. In some embodiments, header 408 may bepermanently installed in the reactor, and have vertical extensions 413.Spargers 406, header 408, and vertical extensions 413 may be a series ofindividual pieces/components to be easily transported and inserted intothe reactor vessel and then individually connected with the vessel. Thesystem depicted in FIG. 4 may include a plurality of headers 408, and aplurality of spargers 406 which may form multiple layers within andalong the vertical of the reactor. Each layer may include a plurality ofannular shrouds 405, and a plurality of spargers 406 fluidly engagedwith a plurality of vertical extensions 413 and header(s) 408. Incertain embodiments, the reactor vessel may include, for example, atleast, greater than, less than, equal to, or any number in between about1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20,21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38,39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56,57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74,75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92,93, 94, 95, 96, 97, 98, 99 to about 100 vertical layers of sets ofspargers, annular shrouds, and headers. In some embodiments, eachvertical layer may include, for example, at least, greater than, lessthan, equal to, or any number in between about 1, 2, 3, 4, 5, 6, 7, 8,9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26,27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44,45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62,63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80,81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98,99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112,113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126,127, 128, 129, 130, 131, 132, 133, 134, 135, 136, 137, 138, 139, 140,141, 142, 143, 144, 145, 146, 147, 148, 149, 150, 151, 152, 153, 154,155, 156, 157, 158, 159, 160, 161, 162, 163, 164, 165, 166, 167, 168,169, 170, 171, 172, 173, 174, 175, 176, 177, 178, 179, 180, 181, 182,183, 184, 185, 186, 187, 188, 189, 190, 191, 192, 193, 194, 195, 196,197, 198, 199 to about 200 spargers and/or annular shrouds. Again, sucha sparger configuration may be employed in reactor systems 400 and 500and 600 described in FIGS. 4, 5, and 6 .

According to other embodiments, spargers 406 may be positioned in abottom portion of the reactor or in a middle portion of the reactor.According to FIG. 4 spargers 406 are oriented in a horizontal position.According to still another embodiment, spargers 406 may be positioned inmultiple positions throughout the reactor to include the upper, middle,and lower portions of the reactor. According to yet another embodiment,spargers 406 may be a ring sparger or a drilled-pipe sparger. Accordingto one embodiment, individual spargers 406 and header 408 may beconfigured as modular components facilitating the ease of reactorconstruction and/or component replacement, general maintenance,cleaning, or allowing for a scalable reactor system depending upon therequirements. In accordance with other embodiments, multiple levels ofspargers 406 and headers 408 may be stacked within the reactor.According to another embodiment, a single level or stack of headers 408may include, for example, at least, greater than, less than, equal to,or any number in between about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12,13, 14, 15, 16, 17, 18, 19 to about 20 individual headers 408. In someembodiments, header 408 may be configured as an annular gas supply.

FIG. 5 , a side view, and FIG. 6 , a top view of FIG. 5 , depict anembodiment where multiple spargers 506 are positioned within the sameannular shroud 505. Having multiple spargers 506 positioned within thesame annular shroud 505 allows for reduced piping and header or manifoldconnections. Similar to FIG. 4 , liquid broth 501 enters the bottom ofreactor 502. Gas substrate is injected into liquid 501 within reactor502 by sparger(s) 506 connected to gas supply/headers 508. At least aportion of the flow of liquid 501 is directed across the exteriorsurface of spargers 506. In some embodiments, nearly all of the flow ofliquid 501 is directed across the exterior surface of spargers 506. Inother embodiment, portions of liquid flow 501 bypasses the exteriorsurface of spargers 506 though passages 503. As the liquid 501 is forcedinto gap 507 defined by the annular shroud 505 and the exterior walls ofthe spargers 506, the liquid is accelerated as it travels across acircumference or vertical surface of the horizontally positionedspargers 506 and the annular shrouds 505. Accelerated liquid 501 ashears injected bubbles on the surface of the spargers 606 breaking theinjected bubbles into fine bubbles 509. Fine bubbles are as describedabove. FIG. 5 and FIG. 6 show three spargers 506 positioned within asingle annular shroud 505. The number of spargers positioned within asingle annular shroud may vary from about 2 to about 10.

Although the present disclosure has been described in certain specificembodiments, many additional modifications and variations would beapparent to those skilled in the art. It is therefore to be understoodthat the present disclosure may be practiced otherwise than specificallydescribed without departing from the scope and spirit of the presentdisclosure. Thus, embodiments of the present disclosure should beconsidered in all respects as illustrative and not restrictive.Accordingly, the scope of the disclosure should be determined not by theembodiments illustrated, but by the appended claims and theirequivalents.

EMBODIMENTS OF THE DISCLOSURE

Embodiment 1. A sparger system for injecting bubbles into a liquidcomprising:

-   -   a support plate;    -   a plurality of annular shrouds engaged with the support plate;        and    -   a plurality of spargers positioned within the annular shrouds to        define a gap between    -   an interior surface of the annular shroud and an exterior        surface of the corresponding sparger, and        wherein the support plate, the annular shrouds, and the spargers        are positioned within the interior of a reactor.

Embodiment 2. The system of embodiment 1 wherein the support plate andthe annular shrouds are integrated into a single component.

Embodiment 3. The system of embodiment 1 or 2 wherein two or morespargers are positioned within a single annular shroud.

Embodiment 4. The system of any of embodiments 1 to 3, wherein a lengthof the spargers is at least 10 cm.

Embodiment 5. The system of any of embodiment 1 to 4, wherein the gap isfrom about 1 mm to about 20 mm.

Embodiment 6. The system of any of embodiments 1 to 5, wherein thesupport plate, the annular shrouds, and the spargers are positioned at atop portion or at a bottom portion of the reactor.

Embodiment 7. The system of any of embodiments 1 to 6, wherein theplurality of spargers engage a plurality of headers, and wherein theplurality of spargers are configured to receive a gas supply from theplurality of headers.

Embodiment 8. The system of any of embodiments 1 to 7, wherein theplurality of headers further comprise a baffle configured to disperse afluid comprising the liquid and bubbles.

Embodiment 9. The system of embodiment 8, wherein the liquid is at leastpartially recirculated liquid.

Embodiment 10. The system of any of embodiments 1 to 9, wherein thesupport plate further comprises a plurality of perforations.

Embodiment 11. The system of any of embodiments 1 to 10, wherein theannular shrouds are positioned within about 20 degrees of a verticalaxis of the reactor.

Embodiment 12. The system of any of embodiments 1 to 11, furthercomprising at least one additional support plate positioned to formmultiple vertical layers within the interior of the reactor, and the atleast one additional support plate engaging the plurality of annularshrouds.

Embodiment 13. The system of any of embodiments 1 10 12, wherein thereactor is a bioreactor.

Embodiment 14. The system of any of embodiments 1 to 12, wherein thereactor is a bioreactor comprising:

-   -   a liquid growth medium;    -   a substrate comprising at least one Cl carbon source, wherein        the plurality of spargers are configured to inject substrate        bubbles into the liquid growth medium; and    -   a culture of at least one microorganism in the liquid growth        medium, wherein the culture of at least one microorganism        anaerobically ferments the substrate to produce at least one        fermentation product.

Embodiment 15. A method of sparging bubbles into a liquid comprising:

-   -   sparging gas into a reactor containing a liquid via a plurality        of spargers positioned within the reactor and configured to emit        bubbles;    -   directing a flow of the liquid across an exterior surface of the        spargers via a plurality of annular shrouds within the reactor        and surrounding the plurality of spargers; and shearing the        bubbles at a surface of the plurality of spargers via the flow        of the liquid across the exterior surface of the spargers.

Embodiment 16. The method of embodiment 15 further comprisingaccelerating the flow of the liquid across the exterior surface of thespargers via a gap formed between an interior surface of the annularshrouds and the exterior surface of the spargers.

Embodiment 17. The method of embodiment 15 or 16, wherein theaccelerated flow of the liquid across the exterior surface of thespargers has a superficial liquid velocity of at least 0.3 m/s.

Embodiment 18. The method of any of embodiments 15 to 17, wherein theaccelerated flow of the liquid across the exterior surface of theplurality of spargers has a velocity of about 0.3 m/s to about 10 m/s.

Embodiment 19. The method of any of embodiments 15 to 18, wherein thesheared bubbles have a diameter of about 0.2 mm to about 2.0 mm.

Embodiment 20. The method of any of embodiments 15 to 19, wherein asuperficial velocity of a gas phase in the vessel is at least 0.03 m/s.

Embodiment 21. The method of any of embodiments 15 to 19, wherein asuperficial velocity of the gas phase in the vessel is about 0.03 m/s toabout 0.1 m/s.

Embodiment 22. The method of any of embodiments 15 to 21, wherein thebubbles are substrate bubbles within a bioreactor containing a liquidgrowth medium, wherein a culture of at least one microorganism in theliquid growth medium aerobically ferments the substrate to produce atleast one fermentation product.

1. A sparger system for injecting bubbles into a liquid comprising: asupport plate; a plurality of annular shrouds engaged with the supportplate; and a plurality of spargers positioned within the annular shroudsto define a gap between an interior surface of the annular shroud and anexterior surface of the corresponding sparger, and wherein the supportplate, the annular shrouds, and the spargers are positioned within theinterior of a reactor.
 2. The system of claim 1 wherein the supportplate and the annular shrouds are integrated into a single component. 3.The system of claim 1 wherein two or more spargers are positioned withina single annular shroud.
 4. The system of claim 1, wherein a length ofthe spargers is at least 10 cm.
 5. The system of claim 1, wherein thegap is from about 1 mm to about 20 mm.
 6. The system of claim 1, whereinthe support plate, the annular shrouds, and the spargers are positionedat a top portion or at a bottom portion of the reactor.
 7. The system ofclaim 1, wherein the plurality of spargers engage a plurality ofheaders, and wherein the plurality of spargers are configured to receivea gas supply from the plurality of headers.
 8. The system of claim 7,wherein the plurality of headers further comprise a baffle configured todisperse a fluid comprising the liquid and bubbles.
 9. The system ofclaim 8, wherein the liquid is at least partially recirculated liquid.10. The system of claim 1, wherein the support plate further comprises aplurality of perforations.
 11. The system of claim 1, wherein theannular shrouds are positioned within about 20 degrees of a verticalaxis of the reactor.
 12. The system of claim 1, further comprising atleast one additional support plate positioned to form multiple verticallayers within the interior of the reactor, and the at least oneadditional support plate engaging the plurality of annular shrouds. 13.The system of claim 1, wherein the reactor is a bioreactor.
 14. Thesystem of claim 1, wherein the reactor is a bioreactor comprising: aliquid growth medium; a substrate comprising at least one C1 carbonsource, wherein the plurality of spargers are configured to injectsubstrate bubbles into the liquid growth medium; and a culture of atleast one microorganism in the liquid growth medium, wherein the cultureof at least one microorganism anaerobically ferments the substrate toproduce at least one fermentation product.
 15. A method of spargingbubbles into a liquid comprising: sparging gas into a reactor containinga liquid via a plurality of spargers positioned within the reactor andconfigured to emit bubbles; directing a flow of the liquid across anexterior surface of the spargers via a plurality of annular shroudswithin the reactor and surrounding the plurality of spargers; andshearing the bubbles at a surface of the plurality of spargers via theflow of the liquid across the exterior surface of the spargers.
 16. Themethod of claim 15 further comprising accelerating the flow of theliquid across the exterior surface of the spargers via a gap formedbetween an interior surface of the annular shrouds and the exteriorsurface of the spargers.
 17. The method of claim 15, wherein theaccelerated flow of the liquid across the exterior surface of thespargers has a superficial liquid velocity of at least 0.3 m/s, or fromabout 0.3 m/s to about to about 10 m/s.
 18. The method of claim 15,wherein the sheared bubbles have a diameter of about 0.2 mm to about 2.0mm.
 19. The method of claim 15, wherein a superficial velocity of a gasphase in the vessel is at least 0.03 m/s, or from about 0.3 m/s to about0.1 m/s.
 20. The method of claim 15, wherein the bubbles are substratebubbles within a bioreactor containing a liquid growth medium, wherein aculture of at least one microorganism in the liquid growth mediumaerobically ferments the substrate to produce at least one fermentationproduct.